Like I said I replaced my thermostat in my 99 F250 LD 5.4 L because I had a leak due to someone not putting the gasket/O-ring in when it was tore down a few weeks back. I had just a slight intermittent miss due to coolant leaking on the wires. I decided to go ahead and put a new thermostat in as long as I was taking it apart to put the O-ring in. After I replaced it and put everything back together it idled really rough and I had no power going down the road.

The codes I amd getting are

P0303 misfire on cylinder 3

P0305 misfire on cylinder 5

P0306 misfire on cylinder 6

P0308 misfire on cylinder 8

P0174 system adaptive fuel too lean on bank 2

Any ideas where I should start to fix this problem?

As I said, my truck was running great for the most part until I replaced the thermostat and gasket to fix a leak. It only had an intermittent miss after running for a long while in the heat. Other than that it was running like a top before I replaced the thermostat???

 

I would start with fixing the misfires as this may correct the other problem for you. Bank 2 would be the driver side bank which appears to be where you have the most misfires.

 

Don't run the motor any length of time with this many cylinders out.
The raw gas passed to the cats will overheat them and melt the substrate, then your in for real hassle and expense on top of the misfires.
Seems like coolant flew all over the place and filled the plug wells.
Remove all the coils and blow out the wells with compressed air. Be sure everything is dry.
Reassemble and test run.
If there are missfires clear the codes and let the PCM tell you which ones are left to address again for bad boots , coils or plugs.
It seems all this was caused by poor workmanship some place along the line.
Good luck.

 

Right you are once again Bluegrass. We blew out the wells and that fixed the last remaining cylinder that was misfiring (#8). I am fortunate that I have a friend who is a ford guy with a salvage yard full of fords. He pulled the COPs and blew them out for me free of charge. The bucking while going up hills in OD is back however. My friend said that all of my COPs are the same age and as I have already had to replace 2, the other ones are probably starting to go as well. He said # 8 is looking pretty rough and is probably about to go. At least I know what causes the bucking now. My plan is to change my remaining coil packs before deer season gets here so I don't have to worry about it then.

Thanks again for the help and info.

 

You have one coil with shorted turns causing the bucking/studder.
It usually won't set a code so you have to hunt for which cylinder is the cause.
I would not let it go to long because it can over current the solidstate switch in the PCM from the lower resistance causing higher current.
The bucking is the low coil output that is now marginal.
Good luck.